SAN JOSE, Calif. — The voice on the other end of the telephone Friday afternoon was that of an 84-year-old nun who sounds 30 years younger and has had as much a hand in Xavier’s remarkable run toward a possible Final Four berth as the man who coaches the team himself.

Without her guidance as the school’s academic adviser, maybe Mack would not have every key player on his 11th-seeded roster, which will take on No. 1 seed Gonzaga in Saturday’s West Region final at the SAP Center with a Final Four the carrot at the end of the stick.

Fleming has not helped Musketeers’ leading scorer Trevon Bluiett refine his scoring skills.

She hasn’t worked with freshman point guard Quentin Goodin on keeping his turnover numbers down.

Nor has she worked with Sean O’Mara on maintaining his position in the paint.

What Fleming has done since she arrived at Xavier in 1983 is allow its basketball players to maintain their scholarships and stay in uniform. Xavier is in the midst of an incredible run during Fleming’s 34 years, with more than 100 consecutive basketball players graduating.

“We haven’t lost a basketball player yet,’’ Fleming told The Post. “And we don’t plan on losing one in the future.’’

Fleming’s duties as an academic adviser began under then-coach Pete Gillen, who gave her the all-encompassing power to overrule the coaches when she believed a player was in need of academic assistance. It was not — and is not — unusual for Fleming to overrule the coaches if she sees the need to do so.

And they all comply. Gillen did. Skip Prosser did. Thad Matta did. Sean Miller did. And now so does Chris Mack, who goes back with Fleming since his days as a player with Xavier.

“She always had veto power and benching power,’’ Mack told The Post on Friday. “She wants to open guys’ eyes to what’s ahead of them after basketball. She’s meant the true definition of the student-athlete. Books come before basketball.’’

Fleming, who belongs to a religious order named “The Sisters of Notre Dame’’ based in France, has never been married nor had children.

“So in many ways,’’ she said, “these are all my children.’’

In 1991, Gillen named Fleming the team’s Most Valuable Player. In 2000, she was inducted into the Xavier athletic hall of fame. She has her own banner hanging in the Cintas Center, Xavier’s home arena.

She attends every home game, goes to many road games and never misses a postseason game.

“The first time I went to an NCAA game I was overcome with all the pomp and circumstance involved with it,’’ she said.

Speaking of pomp, Fleming often sits next to Bill Murray, whose son, Luke, is an Xavier assistant coach. Late in Xavier’s win over Arizona Thursday night, Murray was so overcome with emotion he began rubbing Fleming’s head for luck.

When she started at Xavier as a teacher and got some athletes in her classes, Fleming said: “I realized, ‘Wow, a lot of these kids had not been very well trained in terms of background and study habits.’ They hadn’t developed study skills.

“I didn’t want them to lose their scholarships. So I made up my mind that this is the one chance they have to get a good education and I don’t want them to lose it. I realized that these athletes are under tremendous pressure to produce, and they need time to practice and they need time to study and we have to keep that sacred.”

Fleming watches these games through a different lens than anyone else. She is, of course, a fan. But she is so much more, because she’s invested so much more. She’s invested her life.

Xavier has been to the NCAA Tournament in seven of the eight years Mack has coached. This year marked its fourth Sweet 16 appearance. Now a potential Final Four looms.

It’s impossible to put a number on the amount of games Fleming might have helped the Musketeers win over the years. That never truly can be known. What is known, though, is this: Even at age 84, Fleming has no plans to retire. And that’s good news for Xavier basketball.

“I’ve been tremendously fortunate in my life with good health,’’ she said. “You take what comes to you and someday when God needs me to do something else and be with Him, I’m ready for it.’’

Asked if perhaps she’ll be called to heaven to help God work on His jump shot, Fleming laughed and said, “I’m not sure I can do that.’’